Over-temperature protection circuit, switching power supply circuit and charger

Abstract

The invention discloses an over-temperature protection circuit, a switching power supply circuit and a charger. The over-temperature protection circuit comprises a temperature detection module, a feedback module and a protection control module, the temperature detection module is connected with the protection control module and is used for outputting a protection signal to the protection control module when the area temperature is greater than a preset temperature threshold value; the feedback module is used for outputting a first feedback voltage to the temperature detection module based on the protection signal when the power supply voltage of the power supply end is not less than a preset voltage value so as to maintain the protection signal output state of the temperature detection module; and the protection control module is used for enabling a functional pin of the switching power supply chip to be in a forbidden state based on the protection signal. According to the over-temperature protection circuit, over-temperature protection of the switching power supply chip can be realized without occupying the pin function of the switching power supply chip, and the over-temperature protection false triggering phenomenon in the switching power supply chip is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to an over-temperature protection circuit, a switching power supply circuit and a charger. Background Art

[0002] In a switching power supply, under high power output conditions, the temperature of the internal components of the power supply is prone to rise. If the temperature inside the power supply is too high, the service life of the components may be reduced, or even some components may fail permanently. Therefore, the temperature inside the switching power supply needs to be controlled. The internal temperature detection usually detects the temperature of the area near the internal heating components. When the area temperature is greater than the preset temperature threshold, the power supply is protected.

[0003] Overtemperature protection modes usually include auto (restart) mode and latch (latch) mode. In auto mode, when the protection condition is met, the protection is triggered and the power supply stops working, but when the protection condition is lifted, the power supply immediately resumes normal working state. In latch mode, when the protection condition is met, the protection is triggered and the power supply stops working, but when the protection condition is lifted, the power supply cannot resume normal working state and must resume normal working state after the switching power supply chip is powered off and restarted.

[0004] In the prior art, the switching power supply chip of the switching power supply circuit usually has an over-temperature protection function, and the latch mode can be realized by using the chip itself by configuring the pins. However, in the switching power supply chip, the pin functions are usually multiplexed, and different functions need to be executed in different time periods. This execution method can easily cause the over-temperature protection to be falsely triggered. Summary of the invention

[0005] The embodiments of the present invention provide an over-temperature protection circuit, a switching power supply circuit and a charger to solve the problem that the existing switching power supply chip is prone to erroneously triggering the over-temperature protection.

[0006] An embodiment of the present invention provides an over-temperature protection circuit, including a temperature detection module, a feedback module and a protection control module; The temperature detection module is connected to the power supply terminal of the switching power supply chip and the protection control module, and is used to output a protection signal to the protection control module based on the power supply voltage of the power supply terminal when the regional temperature is greater than a preset temperature threshold; The feedback module is connected to the temperature detection module and also to the connection node between the temperature detection module and the protection control module. It is used to output a first feedback voltage to the temperature detection module when the protection signal is not less than the preset voltage value to maintain the protection signal output state of the temperature detection module, and output a second feedback voltage to the temperature detection module when the protection signal is less than the preset voltage value to stop maintaining the protection signal output state of the temperature detection module; The protection control module is connected to the functional pin of the switching power supply chip and is used to disable the functional pin of the switching power supply chip based on the protection signal.

[0007] Preferably, the temperature detection module includes a reference voltage unit, a temperature detection unit, and a comparator; The reference voltage unit is connected to the non-inverting input terminal of the comparator and is used to output a reference voltage to the comparator; The temperature detection unit is connected to the inverting input terminal of the comparator and is used to output a temperature detection voltage to the comparator based on the regional temperature; The power supply terminal of the comparator is connected to the power supply terminal of the switching power supply chip, and the output terminal of the comparator is connected to the protection control module. It is used to output a protection signal to the protection control module based on the supply voltage of the power supply terminal when the reference voltage is greater than the temperature detection voltage; The feedback module is connected to the output terminal and the non-inverting input terminal of the comparator.

[0008] Preferably, the reference voltage unit includes a reference source, a first voltage dividing resistor, and a second voltage dividing resistor; The first end of the first voltage dividing resistor is connected to the reference source, the second end of the first voltage dividing resistor is connected to the non-inverting input terminal of the comparator and the first end of the second voltage dividing resistor, and the second end of the second voltage dividing resistor is grounded.

[0009] Preferably, the temperature detection unit includes a third voltage dividing resistor and a thermistor; The first end of the third voltage dividing resistor is connected to the reference source, the second end of the third voltage dividing resistor is connected to the inverting input terminal of the comparator and the first end of the thermistor, and the second end of the thermistor is grounded.

[0010] Preferably, the reference source includes a voltage stabilizing component and a pull-up resistor; The first end of the voltage stabilizing component is connected to the power supply terminal of the switching power supply chip through the pull-up resistor, and the second end of the voltage stabilizing component is grounded; The first ends of the first voltage dividing resistor and the third voltage dividing resistor are both connected to the connection node between the voltage stabilizing component and the pull-up resistor.

[0011] Preferably, the feedback module includes a feedback resistor; The first end of the feedback resistor is connected to the output end of the comparator, and the second end of the feedback resistor is connected to the non-inverting input end of the comparator.

[0012] Preferably, the protection control module includes a current-limiting resistor and a switching transistor; The first end of the current-limiting resistor is connected to the temperature detection module, and the second end of the current-limiting resistor is connected to the control end of the switching transistor; The first end of the switching transistor is connected to the functional pin of the switching power supply chip, and the second end of the switching transistor is grounded.

[0013] Preferably, the functional pin includes at least one of a PWM control pin, a signal sampling pin, and a feedback pin.

[0014] An embodiment of the present invention further provides a switching power supply circuit, including a rectification module, a transformer, an auxiliary winding, a switching power supply chip, and the over-temperature protection circuit according to any one of the above; The first end of the rectification module is used to connect to the mains circuit, the second end of the rectification module is used to be connected to the input end of the transformer, and the output end of the transformer is used to connect to an external device; The switching power supply chip is connected to the transformer and is used to control the transformer to output electric energy to the external device; The auxiliary winding is coupled to the transformer and is also connected to the power supply end of the switching power supply chip to provide a supply voltage for the switching power supply chip; The over-temperature protection circuit is connected to the functional pin of the switching power supply chip and is used to disable the functional pin of the switching power supply chip when the regional temperature is greater than a preset temperature threshold.

[0015] An embodiment of the present invention further provides a charger, including the above-mentioned switching power supply circuit.

[0016] The over-temperature protection circuit, the switching power supply circuit, and the charger provided by the embodiments of the present invention can realize the over-temperature protection of the switching power supply chip without occupying the pin functions of the switching power supply chip by setting an over-temperature protection circuit connected to the switching power supply chip and including a temperature detection module, a feedback module, and a protection control module, and prevent the phenomenon of false triggering of over-temperature protection in the switching power supply chip. Description of the Drawings

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] Figure 1 is a schematic circuit diagram of an over-temperature protection circuit in an embodiment of the present invention; Figure 2 is a schematic circuit diagram of a switching power supply circuit in an embodiment of the present invention.

[0019] In the figure: 1. Temperature detection module; 11. Reference voltage unit; 111. Reference source; 12. Temperature detection unit; 2. Feedback module; 3. Protection control module. Detailed implementation manners

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0021] It should be understood that the present invention can be implemented in different forms and should not be construed as limited to the embodiments presented here. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals throughout the drawings denote the same elements.

[0022] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be denoted as the second element, component, region, layer or part.

[0023] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. may be used herein for convenience of description to describe the relationship of one element or feature shown in the figures with other elements or features. It should be understood that, in addition to the orientation shown in the figures, the spatial relationship terms are also intended to include different orientations of the device in use and operation. For example, if the device in the figures is flipped, then an element or feature described as "under other elements" or "beneath them" or "under it" will be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "beneath" can include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are to be interpreted accordingly.

[0024] The purpose of the terms used herein is only to describe specific embodiments and not to limit the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. As used herein, the term "and / or" includes any and all combinations of the associated listed items.

[0025] To fully understand the present invention, detailed structures and steps will be set forth in the following description to explain the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may have other embodiments.

[0026] An embodiment of the present invention provides an over-temperature protection circuit, as Figure 1 shown, comprising a temperature detection module 1, a feedback module 2 and a protection control module 3; the temperature detection module 1 is connected to the power supply terminal VCC of the switch power supply chip IC1 and the protection control module 3, and is configured to output a protection signal to the protection control module 3 based on the supply voltage of the power supply terminal VCC when the regional temperature is greater than a preset temperature threshold; the feedback module 2 is connected to the temperature detection module 1 and is also connected to the connection node between the temperature detection module 1 and the protection control module 3, and is configured to output a first feedback voltage to the temperature detection module 1 to maintain the protection signal output state of the temperature detection module 1 when the protection signal is not less than a preset voltage value, and output a second feedback voltage to the temperature detection module 1 to stop maintaining the protection signal output state of the temperature detection module 1 when the protection signal is less than the preset voltage value; the protection control module 3 is connected to the functional pin of the switch power supply chip IC1, and is configured to disable the functional pin of the switch power supply chip IC1 based on the protection signal.

[0027] As an example, the over-temperature protection circuit includes a temperature detection module 1, a feedback module 2, and a protection control module 3. The temperature detection module 1 is connected to the power supply terminal VCC of the switching power supply chip IC1 and the protection control module 3. When the current regional temperature is greater than the preset temperature threshold, the temperature detection module 1 can output a protection signal to the protection control module 3 based on the supply voltage of the power supply terminal VCC, and the voltage value of the protection signal is equal to or linearly converted with the supply voltage provided by the power supply terminal VCC of the switching power supply chip IC1.

[0028] When receiving the protection signal, the protection control module 3 can disable the function pins of the switching power supply chip IC1. For example, it pulls down the function pins connected thereto to the ground, making the function pins in a disabled state, that is, a state where they cannot execute the corresponding functions. When the protection control module 3 does not receive the protection signal, the function pins of the switching power supply chip IC1 will not be disabled, and the function pins of the switching power supply chip IC1 can normally execute the corresponding functions.

[0029] The feedback module 2 is connected to the temperature detection module 1 and also to the connection node between the temperature detection module 1 and the protection control module 3. When the temperature detection module 1 outputs a protection signal to the protection control module 3, since the voltage value of the protection signal is equal to or linearly converted with the supply voltage provided by the power supply terminal VCC of the switching power supply chip IC1, when the feedback module 2 determines the feedback voltage based on the protection signal, it actually forms positive feedback on the output of the temperature detection module 1 based on the supply voltage of the power supply terminal VCC. Specifically, if the voltage value of the protection signal is equal to the supply voltage of the power supply terminal VCC, when the supply voltage of the power supply terminal VCC is not less than the preset voltage value, the feedback module 2 outputs a first feedback voltage with a higher voltage value to the temperature detection module 1, and the first feedback voltage can keep the temperature detection module 1 in the protection signal output state, that is, regardless of whether the regional temperature is greater than the preset temperature threshold, the temperature detection module 1 always outputs a protection signal, making the function pins of the switching power supply chip IC1 continuously in the disabled state; when the supply voltage of the power supply terminal VCC is less than the preset voltage value, the feedback module 2 outputs a second feedback voltage with a smaller value to the temperature detection module 1, and the second feedback voltage is not sufficient to keep the temperature detection module 1 in the protection signal output state. At this time, if the regional temperature is not greater than the preset temperature threshold, the temperature detection module 1 will not output a protection signal anymore, and the function pins of the switching power supply chip IC1 can return to the normal state.

[0030] Among them, the preset voltage value is related to the voltage threshold at which the switching power supply chip IC1 enters the restart state. If the voltage value of the protection signal is equal to the supply voltage of the power supply terminal VCC, the preset voltage value is equal to the voltage threshold at which the switching power supply chip IC1 enters the restart state. When the protection signal is not less than the preset voltage value, the switching power supply chip IC1 is in the normal working state. When the protection signal is less than the preset voltage value, the switching power supply chip IC1 will enter the restart state. When the voltage value of the protection signal is equal to the supply voltage of the power supply terminal VCC and the preset voltage value is the voltage threshold at which the switching power supply chip IC1 enters the restart state, once the regional temperature is greater than the preset temperature threshold, the temperature detection module 1 will continuously output the protection signal, making the functional pin of the switching power supply chip IC1 connected to the protection control module 3 always in the disabled state until the supply voltage is less than the preset voltage value. After the switching power supply chip IC1 restarts, the temperature detection module 1 will no longer continuously output the protection signal, and the functional pin of the switching power supply chip IC1 connected to the protection control module 3 can be released from the disabled state, realizing the latch protection mode of over-temperature protection.

[0031] In this example, by setting an over-temperature protection circuit connected to the switching power supply chip IC1 and including the temperature detection module 1, the feedback module 2, and the protection control module 3, over-temperature protection of the switching power supply chip IC1 can be achieved without occupying the pin functions of the switching power supply chip IC1, preventing false triggering of over-temperature protection in the switching power supply chip IC1.

[0032] In an embodiment, the temperature detection module 1 includes a reference voltage unit 11, a temperature detection unit 12, and a comparator U1; the reference voltage unit 11 is connected to the non-inverting input terminal of the comparator U1 and is used to output a reference voltage to the comparator U1; the temperature detection unit 12 is connected to the inverting input terminal of the comparator U1 and is used to output a temperature detection voltage to the comparator U1 based on the regional temperature; the power supply terminal of the comparator U1 is connected to the power supply terminal VCC of the switching power supply chip IC1, and the output terminal of the comparator U1 is connected to the protection control module 3 and is used to output a protection signal to the protection control module 3 based on the supply voltage of the power supply terminal VCC when the reference voltage is greater than the temperature detection voltage; the feedback module 2 is connected to the output terminal and the non-inverting input terminal of the comparator U1.

[0033] As an example, the temperature detection module 1 includes a reference voltage unit 11, a temperature detection unit 12, and a comparator U1. The reference voltage unit 11 is connected to the non-inverting input terminal of the comparator U1 and is used to output a constant reference voltage to the comparator U1. The temperature detection unit 12 is connected to the inverting input terminal of the comparator U1 and is used to quantify the current regional temperature into a corresponding temperature detection voltage and output it to the comparator U1. In this embodiment, the regional temperature may be inversely proportional to the temperature detection voltage. When the regional temperature is higher, the temperature detection voltage is smaller. The power supply terminal of the comparator U1 is connected to the power supply terminal VCC of the switching power supply chip IC1. The output terminal of the comparator U1 is connected to the protection control module 3. When the reference voltage is not greater than the temperature detection voltage, it indicates that the current regional temperature is not greater than the preset temperature threshold. At this time, the comparator U1 outputs a low level and does not output a protection signal. When the reference voltage is greater than the temperature detection voltage, it indicates that the current regional temperature is greater than the preset temperature threshold. At this time, the comparator U1 can generate a level flip and output a high-level signal, that is, a protection signal, to the protection control module 3 based on the supply voltage of the power supply terminal VCC.

[0034] The feedback module 2 is connected to the output terminal and the non-inverting input terminal of the comparator U1. When the comparator U1 outputs a high-level signal, that is, a protection signal, since the voltage value of the protection signal is equal to or linearly converted with the supply voltage of the power supply terminal VCC of the switching power supply chip IC1, the feedback module 2 can output a feedback voltage to the non-inverting input terminal of the comparator U1 based on the supply voltage of the power supply terminal VCC, forming positive feedback on the output of the temperature detection module 1. If the voltage value of the protection signal is equal to the supply voltage of the power supply terminal VCC of the switching power supply chip IC1, when the supply voltage of the power supply terminal VCC is not less than the preset voltage value, the feedback module 2 outputs a first feedback voltage with a higher voltage value to the non-inverting input terminal of the comparator U1 to reduce the regional temperature to the normal level. When the temperature detection voltage input by the temperature detection unit 12 to the inverting input terminal of the comparator U1 becomes larger again, the input of the non-inverting input terminal of the comparator U1 is still greater than the input of the inverting input terminal of the comparator U1, so that the comparator U1 continuously outputs a high level, that is, a protection signal. When the supply voltage of the power supply terminal VCC is less than the preset voltage value, the feedback module 2 outputs a second feedback voltage with a lower voltage value to the non-inverting input terminal of the comparator U1. When the regional temperature is reduced to the normal level and the temperature detection voltage input by the temperature detection unit 12 to the inverting input terminal of the comparator U1 becomes larger again, the second feedback voltage cannot keep the input of the non-inverting input terminal of the comparator U1 in a state greater than the input of the inverting input terminal. The comparator U1 will return to the low-level output state and no longer output a protection signal.

[0035] In one embodiment, the reference voltage unit 11 includes a reference source 111, a first voltage dividing resistor R1, and a second voltage dividing resistor R2. The first end of the first voltage dividing resistor R1 is connected to the reference source 111. The second end of the first voltage dividing resistor R1 is connected to the non-inverting input terminal of the comparator U1 and the first end of the second voltage dividing resistor R2. The second end of the second voltage dividing resistor R2 is grounded.

[0036] As an example, the reference voltage unit 11 includes a reference source 111, a first voltage dividing resistor R1, and a second voltage dividing resistor R2. The first end of the first voltage dividing resistor R1 is connected to the reference source 111. The second end of the first voltage dividing resistor R1 is connected to the non-inverting input terminal of the comparator U1 and the first end of the second voltage dividing resistor R2. The second end of the second voltage dividing resistor R2 is grounded. The reference source 111 is used to provide a reference voltage Vref. The first voltage dividing resistor R1 and the second voltage dividing resistor R2 divide the voltage provided by the reference source 111, so that the voltage input to the non-inverting input terminal of the comparator U1 is equal to the voltage across the second voltage dividing resistor R2, that is .

[0037] In one embodiment, the temperature detection unit 12 includes a third voltage dividing resistor R3 and a thermistor Rx. The first end of the third voltage dividing resistor R3 is connected to the reference source 111. The second end of the third voltage dividing resistor R3 is connected to the inverting input terminal of the comparator U1 and the first end of the thermistor Rx. The second end of the thermistor Rx is grounded.

[0038] As an example, the temperature detection unit 12 includes a third voltage dividing resistor R3 and a thermistor Rx. The first end of the third voltage dividing resistor R3 is connected to the reference source 111. The second end of the third voltage dividing resistor R3 is connected to the inverting input terminal of the comparator U1 and the first end of the thermistor Rx. The second end of the thermistor Rx is grounded. The third voltage dividing resistor R3 and the thermistor Rx divide the reference voltage Vref provided by the reference source 111, so that the temperature detection voltage input to the non-inverting input terminal of the comparator U1 is equal to the voltage across the thermistor Rx, that is , the resistance value of the thermistor Rx can change according to the regional temperature change. When the regional temperature rises, the resistance value of the thermistor Rx decreases, and the temperature detection voltage input to the inverting input terminal of the comparator U1 also decreases accordingly. When the regional temperature does not rise above the preset temperature threshold, , the comparator U1 outputs a low level. When the regional temperature rises above the preset temperature threshold, the temperature detection voltage input to the inverting input terminal of the comparator U1 will be less than the reference voltage input to the non-inverting input terminal of the comparator U1, , the output of the comparator U1 has a level inversion, changing from outputting a low level signal to outputting a high level signal, that is, the protection signal.

[0039] In one embodiment, the reference source 111 includes a voltage regulator component and a pull-up resistor R4; a first end of the voltage regulator component is connected to a power supply terminal VCC of the switching power supply chip IC1 through the pull-up resistor R4, and a second end of the voltage regulator component is grounded; a first end of the first voltage-dividing resistor R1 and a first end of the third voltage-dividing resistor R3 are both connected to a connection node between the voltage regulator component and the pull-up resistor R4.

[0040] As an example, the reference source 111 may include a voltage regulator component and a pull-up resistor R4. A first end of the voltage regulator component is connected to a power supply terminal VCC of the switching power supply chip IC1 through the pull-up resistor R4, and a second end of the voltage regulator component is grounded; a first end of the first voltage-dividing resistor R1 and a first end of the third voltage-dividing resistor R3 are both connected to a connection node between the voltage regulator component and the pull-up resistor R4. The voltage regulator component may be a TL431 type precision controllable voltage regulator source. The cathode and the reference electrode of the TL431 are connected to the pull-up resistor R4, and the anode of the TL431 is grounded. The voltage across its two ends can be stabilized at a fixed value, such as 2.5V, so that a stable and unchanging reference voltage can be obtained in the reference voltage unit 11.

[0041] As another example, the reference source 111 may also be an internal reference source of the switching power supply chip IC1 or in the switching power supply circuit where the switching power supply chip IC1 is located.

[0042] In one embodiment, the feedback module 2 includes a feedback resistor R5; a first end of the feedback resistor R5 is connected to an output terminal of the comparator U1, and a second end of the feedback resistor R5 is connected to a non-inverting input terminal of the comparator U1.

[0043] As an example, the feedback module 2 includes a feedback resistor R5. A first end of the feedback resistor R5 is connected to an output terminal of the comparator U1, and a second end of the feedback resistor R5 is connected to a non-inverting input terminal of the comparator U1. In an actual circuit, as Figure 1 shown, a power supply terminal VCC of the comparator U1 is connected to a power supply terminal VCC of the switching power supply chip IC1 to receive the supply voltage of the switching power supply chip IC1. Since the comparator U1 is actually composed of switching transistors inside, the output voltage value of the comparator U1 when the level flips to a high level is related to the voltage input to the power supply terminal VCC of the comparator U1, that is, the voltage value of the protection signal output by the comparator U1 is equal to or linearly converted with the supply voltage of the power supply terminal VCC of the switching power supply chip IC1. Therefore, when the comparator U1 outputs a high level, the feedback voltage input by the feedback resistor R5 to the non-inverting input terminal of the comparator U1 is associated with the supply voltage of the power supply terminal VCC of the switching power supply chip IC1.

[0044] When the regional temperature is greater than the preset temperature threshold, causing the voltage across the thermistor Rx in the temperature detection unit 12 to drop and the comparator U1 to output a high-level signal, according to the superposition principle, the feedback voltage fed back by the feedback resistor R5 to the non-inverting input terminal of the comparator U1 is , and at this time, the voltage at the input terminal of the comparator U1 satisfies . By adjusting the resistance parameters of the feedback resistor R5, the first voltage-dividing resistor R1, the second voltage-dividing resistor R2, etc., when the voltage value of the protection signal is greater than the preset voltage value, always holds. That is, once the regional temperature is greater than the preset temperature threshold, the temperature detection module 1 continuously outputs a protection signal, causing the functional pin of the switching power supply chip IC1 connected to the protection control module 3 to always be in the disabled state. It is not until the protection signal is less than the preset voltage value and the switching power supply chip IC1 restarts that the temperature detection module 1 no longer continuously outputs the protection signal, and the functional pin of the switching power supply chip IC1 connected to the protection control module 3 is released from the disabled state, realizing the latch protection mode for over-temperature protection. Among them, the resistance value range of Rx is 2K~200K.

[0045] In an embodiment, the protection control module 3 includes a current-limiting resistor R6 and a switching transistor Q1; the first end of the current-limiting resistor R6 is connected to the temperature detection module 1, and the second end of the current-limiting resistor R6 is connected to the control end of the switching transistor Q1; the first end of the switching transistor Q1 is connected to the functional pin of the switching power supply chip IC1, and the second end of the switching transistor Q1 is grounded.

[0046] As an example, the protection control module 3 includes a current-limiting resistor R6 and a switching transistor Q1. The switching transistor Q1 can be an NPN-type triode. The first end of the switching transistor Q1 is the collector of the NPN-type triode, the second end of the switching transistor Q1 is the emitter of the NPN-type triode, the control end of the switching transistor Q1 is the base of the NPN-type triode. The first end of the current-limiting resistor R6 is connected to the temperature detection module 1, and the second end of the current-limiting resistor R6 is connected to the control end of the switching transistor Q1. The first end of the switching transistor Q1 is connected to the functional pin of the switching power supply chip IC1, and the second end of the switching transistor Q1 is grounded. When the regional temperature is greater than the preset temperature threshold, the comparator U1 in the temperature detection module 1 can output a protection signal. The existence of the feedback resistor R5 enables the comparator U1 to continuously maintain the protection signal output state when the supply voltage is not less than the preset voltage value, that is, continuously output a high level. The high level can turn on the switching transistor Q1 in the protection control module 3, pull down the functional pin of the switching power supply chip IC1 connected to the switching transistor Q1 to the ground, so that this functional pin cannot normally output or receive signals, and the pin function is disabled. When the comparator U1 continuously maintains the protection signal output state, if the supply voltage is less than the preset voltage value and the switching power supply chip IC1 restarts, the feedback effect of the feedback resistor R5 on the comparator U1 is released, and the comparator U1 no longer continuously maintains the protection signal output state. At this time, if the regional temperature is not greater than the preset temperature threshold, the comparator U1 outputs a low-level signal, the switching transistor Q1 is turned off, and the functional pin of the switching power supply chip IC1 connected to the switching transistor Q1 is no longer pulled down to the ground and can normally output or receive signals.

[0047] In one embodiment, the functional pin includes at least one of a PWM control pin GATE, a signal sampling pin CS, and a feedback pin FB.

[0048] As an example, the functional pin of the switching power supply chip IC1 connected by the over-temperature protection circuit can be at least one of a PWM control pin GATE, a signal sampling pin CS, and a feedback pin FB, and can be selected to be connected to the corresponding functional pin according to the control requirements to perform corresponding protection on the switching power supply circuit during over-temperature.

[0049] An embodiment of the present invention further includes a switching power supply circuit, which includes a rectification module, a transformer, an auxiliary winding, a switching power supply chip IC1, and the over-temperature protection circuit in any one of the above embodiments; the first end of the rectification module is used to connect to the mains circuit, the second end of the rectification module is used to be connected to the input end of the transformer, and the output end of the transformer is used to connect to an external device; the switching power supply chip IC1 is connected to the transformer and is used to control the transformer to output electric energy to the external device; the auxiliary winding is coupled with the transformer and is also connected to the power supply terminal VCC of the switching power supply chip IC1 to provide a supply voltage for the switching power supply chip IC1; the over-temperature protection circuit is connected to the functional pin of the switching power supply chip IC1 and is used to disable the functional pin of the switching power supply chip IC1 when the regional temperature is greater than a preset temperature threshold.

[0050] As an example, the switching power supply circuit includes a rectification module, a transformer, an auxiliary winding, a switching power supply chip IC1, and the over-temperature protection circuit in any one of the above embodiments; the first end of the rectification module is used to connect to the mains circuit, the second end of the rectification module is used to be connected to the input end of the transformer, and the output end of the transformer is used to connect to an external device; the switching power supply chip IC1 is connected to the transformer and is used to control the transformer to output electric energy to the external device; the auxiliary winding is coupled with the transformer and is also connected to the power supply terminal VCC of the switching power supply chip IC1 to provide a supply voltage for the switching power supply chip IC1; the over-temperature protection circuit is connected to the functional pin of the switching power supply chip IC1. When the regional temperature is greater than the preset temperature threshold, the comparator U1 in the temperature detection module 1 can output a protection signal. The existence of the feedback module 2 enables the comparator U1 to continuously maintain the protection signal output state when the protection signal is not less than the preset voltage value, that is, continuously output a high level. The high level can make the switch Q1 in the protection control module 3 conduct, pull down the functional pin of the switching power supply chip IC1 connected to the switch Q1 to the ground, so that the functional pin cannot normally output or receive signals, and the pin function is disabled. When the comparator U1 continuously maintains the protection signal output state, if the switching power supply chip IC1 restarts, the supply voltage of the power supply terminal VCC of the power supply chip IC1 will also drop to be less than the voltage threshold for entering the restart state, then the protection signal output by the temperature detection module 1 will also be less than the preset voltage value, and the feedback effect of the feedback resistor R5 on the comparator U1 will be lifted, and the comparator U1 will no longer continuously maintain the protection signal output state. At this time, if the regional temperature is not greater than the preset temperature threshold, the comparator U1 outputs a low-level signal, the switch Q1 is turned off, and the functional pin of the switching power supply chip IC1 connected to the switch Q1 is no longer pulled down to the ground and can normally output or receive signals.

[0051] In this example, by setting an over-temperature protection circuit connected to the switching power supply chip IC1 and including a temperature detection module 1, a feedback module 2, and a protection control module 3, over-temperature protection of the switching power supply chip IC1 can be achieved without occupying the pin functions of the switching power supply chip IC1, preventing false triggering phenomena from occurring in the switching power supply chip IC1.

[0052] The embodiment of the present invention further includes a charger, including the switching power supply circuit in the above embodiment.

[0053] The above-described embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention and should all be included within the protection scope of the present invention.

Claims

1. An over-temperature protection circuit, characterized in that, It includes a temperature detection module, a feedback module, and a protection control module; The temperature detection module is connected to the power supply terminal of the switching power supply chip and the protection control module, and is configured to output a protection signal to the protection control module based on the supply voltage of the power supply terminal when the regional temperature is greater than a preset temperature threshold; The feedback module is connected to the temperature detection module and is also connected to the connection node between the temperature detection module and the protection control module. It is configured to output a first feedback voltage to the temperature detection module to maintain the protection signal output state of the temperature detection module when the protection signal is not less than a preset voltage value, and output a second feedback voltage to the temperature detection module to stop maintaining the protection signal output state of the temperature detection module when the protection signal is less than the preset voltage value; The protection control module is connected to the functional pin of the switching power supply chip and is configured to make the functional pin of the switching power supply chip in a disabled state based on the protection signal.

2. The over-temperature protection circuit according to claim 1, wherein The temperature detection module includes a reference voltage unit, a temperature detection unit, and a comparator; The reference voltage unit is connected to the non-inverting input terminal of the comparator and is configured to output a reference voltage to the comparator; The temperature detection unit is connected to the inverting input terminal of the comparator and is configured to output a temperature detection voltage to the comparator based on the regional temperature; The power supply terminal of the comparator is connected to the power supply terminal of the switching power supply chip, and the output terminal of the comparator is connected to the protection control module. It is configured to output a protection signal to the protection control module based on the supply voltage of the power supply terminal when the reference voltage is greater than the temperature detection voltage; The feedback module is connected to the output terminal and the non-inverting input terminal of the comparator.

3. The over-temperature protection circuit according to claim 2, wherein The reference voltage unit includes a reference source, a first voltage dividing resistor, and a second voltage dividing resistor; The first end of the first voltage dividing resistor is connected to the reference source, the second end of the first voltage dividing resistor is connected to the non-inverting input terminal of the comparator and the first end of the second voltage dividing resistor, and the second end of the second voltage dividing resistor is grounded.

4. The over-temperature protection circuit according to claim 3, wherein, The temperature detection unit includes a third voltage dividing resistor and a thermistor; The first end of the third voltage dividing resistor is connected to the reference source, the second end of the third voltage dividing resistor is connected to the inverting input terminal of the comparator and the first end of the thermistor, and the second end of the thermistor is grounded.

5. The over-temperature protection circuit according to claim 4, wherein The reference source includes a voltage stabilizing component and a pull-up resistor; The first end of the voltage stabilizing component is connected to the power supply terminal of the switching power supply chip through the pull-up resistor, and the second end of the voltage stabilizing component is grounded; The first ends of the first voltage dividing resistor and the third voltage dividing resistor are both connected to the connection node between the voltage stabilizing component and the pull-up resistor.

6. The over-temperature protection circuit according to claim 2, characterized in that, The feedback module includes a feedback resistor; The first end of the feedback resistor is connected to the output terminal of the comparator, and the second end of the feedback resistor is connected to the non-inverting input terminal of the comparator.

7. The over-temperature protection circuit according to claim 1, wherein The protection control module includes a current limiting resistor and a switching tube; The first end of the current limiting resistor is connected to the temperature detection module, and the second end of the current limiting resistor is connected to the control terminal of the switching tube; The first end of the switching transistor is connected to the functional pin of the switching power supply chip, and the second end of the switching transistor is grounded.

8. The over-temperature protection circuit according to claim 1, characterized in that, The functional pin includes at least one of a PWM control pin, a signal sampling pin, and a feedback pin.

9. A switching power supply circuit, characterized in that, It includes a rectification module, a transformer, an auxiliary winding, a switching power supply chip, and the over-temperature protection circuit according to any one of claims 1-8; The first end of the rectification module is used to connect to the mains circuit, the second end of the rectification module is used to be connected to the input end of the transformer, and the output end of the transformer is used to connect to an external device; The switching power supply chip is connected to the transformer and is used to control the transformer to output electric energy to an external device; The auxiliary winding is coupled with the transformer and is also connected to the power supply end of the switching power supply chip to provide a supply voltage for the switching power supply chip; The over-temperature protection circuit is connected to the functional pin of the switching power supply chip and is used to disable the functional pin of the switching power supply chip when the regional temperature is greater than a preset temperature threshold.

10. A charger, characterized in that, It includes the switching power supply circuit according to claim 9.

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